An elastomeric vial cap used for sealing a vial container, but allowing pipette access to its containment fluid includes an annular flange portion for capping the vial and a sloped truncated cone portion to easily guide the pipette into the vial container. A tubular seal portion is configured to encircle the truncated cone portion and firmly engage an inside wall of the vial container with ease of insertion. A center flap portion is circumscribed by a channel at its top surface for penetration by the pipette and has a flex portion. The center flap portion separates around the perimeter of the channel but hinges at the channel above the flex portion and does not become dislodged. The ratio of the diameters of the pipette and the center flap portion is such that significant problems related to back-pressure and vacuum conditions do not exist during transfer of the containment fluid.
